Photographic process with improved activator composition

ABSTRACT

An improved photographic process for developing a photographic element having a silver halide emulsion layer with silver halide developing agents disposed therein or contiguous thereto as a separate layer comprising (1) exposing said photographic element and (2) applying to the exposed element an alkaline activator composition containing a small amount of a thiosulfate, preferably an alkali or alkaline earth metal or ammonium thiosulfate, having a concentration of from 2 to 20 grams per liter. It is believed that the thiosulfate causes unexposed silver halide to dissolve and plate on the image area simultaneously with chemical development, thereby creating a blue-black image tone of increased maximum density and sharpness.

United States Patent [72] Inventor John R. Kane Pitt-rd, N.Y.

21 Appl. No. 722,551

[22] Filed Apr. 19,1968

[45] Patented Nov. 23, 1971 [73] Assignee Itek Corporation Lexington, Mass.

[54] PHOTOGRAPI-IIC PROCESS WITH IMPROVED ACTIVATOR COMPOSITION 16 Claims, No Drawings [51] Int. Cl G03c 5/30 [50] Field ofSearch ..96/6l, 66.3,

66, 76, 63, 95 [56] References Cited UNITED STATES PATENTS 3,395,015 7/1968 Willems et al. 96/76 X 3,392,019 7/1968 Barnes etal. 96/95 Altomeys-Homer 0. Blair, Robert L. Nathans and W. Gary Goodson ABSTRACT: An improved photographic process for developing a photographic element having a silver halide emulsion layer with silver halide developing agents disposed therein or contiguous thereto as a separate layer comprising I) exposing said photographic element and (2) applying to the exposed element an alkaline activator composition containing a small amount of a thiosulfate, preferably an alkali or alkaline earth metal or ammonium thiosulfate, having a concentration of from 2 to 20 grams per liter. It is believed that the thiosulfate causes unexposed silver halide to dissolve and plate on the image area simultaneously with chemical development, thereby creating a blue-black image tone of increased maximum density and sharpness.

PHOTOGRAPI-IIC PROCESS WITII IMPROVED ACTIVATOR COMPOSITION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the field of photography, and more specifically, to a photographic process for developing a photographic element comprising a silver halide emulsion layer having developing agents disposed therein or contiguous thereto as a separate layer, using an improved activator solution.

2. Description of the Prior Art.

In the usual process of photographic development, an exposed photographic element comprising a support having a silver halide emulsion layer thereon is immersed in a developing bath containing a silver halide photographic developing agent. The developing bath is normally maintained as a separate processing bath and with continuous usef the bath becomes depleted and less efficient so that special techniques and replenishments are normally required to maintain optimum processing efficiency. The developing baths of the prior art normally contain a developing agent, a preservative such as sodium sulfite, and alkali to activate the developing agent, and may also contain other materials, such as sodium bromide as a restrainer.

In order to eliminate the problems associated with the aforementioned developing baths, the prior art has resorted to incorporating various photographic developing agents and their precursors into the silver halide emulsion layer of the photographic element, or into layers adjacent thereto. Photographic elements of this nature are described in detail in U.S. Pat. Nos. 3,29l,609; 3,262,781; 3,246,988; 3,192,046; Canadian Patent 766,708 and United Kingdom Patent 1,045,303.

To develop a photographic element containing developers in or adjacent to the silver halide emulsion, the element is exposed to an original or reproduction and developed by treating the exposed emulsion layer with an alkaline activator bath, such as sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide etc.; having a pH of at least about 9.0 and preferably of at least about 10.5. The photographic element is then stabilized by conventional fixation such as by sodium thiosulfate or ammonium thiocyanate. Photographic elements of this nature developed with an alkaline activator solution generally produce images having a brown-black tone rather than a desired blue-black tone.

STATEMENT OF THE INVENTION It has now been unexpectedly found that a photographic element comprising a photographic developer or its precursor in the photographic silver halide emulsion layer or in a layer contiguous thereto, or both, may be processed to produce images of a blue-black tone with increased maximum density and sharpness when contacted with an alkaline activator solution containing a thiosulfate, and especially a thiosulfate of an alkali or alkaline earth metal or ammonium, preferably having a concentration of from 2 to 20 grams per liter of solution. More particularly, this invention involves a process for developing a photographic element comprising a photographic developer or its precursor in the photographic silver halide emulsion layer or in a layer contiguous thereto, or both, wherein the improvement comprises applying to an exposed photographic element an alkaline activator solution containing a thiosulfate such as an alkali or alkaline earth or ammonium thiosulfate, wherein the concentration is as above described. The overall process for developing a photographic element in accordance with the invention comprises the steps of exposing the photographic element to a positive or negative image, development by applying an alkaline activator solution containing a small amount of a thisoulfate to the exposed element, stabilization by application of a conventional fixation solution, rinsing with water and drying.

DESCRIPTION OF PREFERRED EMBODIMENT (s) The photographic silver halide emulsions useful for the formation of photographic elements processed with the activator compositions of this invention include any of the known silver halide developing out emulsions, such as silver-chloride, chlorobromide, -chloroiodide, -chlorobromoiodide, -bromide, and -bromoiodide developing out emulsions. Any of the known water-permeable hydrophilic colloids can be used with the silver halide emulsions, or in layers contiguous thereto. Typical water-permeable hydrophilic colloids include gelatin, albumin, polyvinyl alcohol agar agar, sodium alginate, hydrolyzed cellulose esters, hydrophilic polyvinyl copolymers, etc.

The photographic elements also contain developing agents for the silver halide emulsion, either dispersed in the emulsion itself, coated on the emulsion as a separate layer dispersed in a water-permeable hydrophilic colloid binder, or both. I-Iydroquinone and substituted hydroquinones are exemplary of the developers that may be used in photographic elements of this nature. The substituted hydroquinones include alkylsubstituted hydroquinones, aryl-substituted hydroquinones and other hydrocarbon substituted hydroquinones, carboxylsubstituted hydroquinones, acyl-substituted hydroquinones, acyloxy-substituted hydroquinones, alkoxy-substituted hydroquinones, halo-substituted hydroquinones, etc. A number of 3'pyrazolidones are also used as silver halide developing agents including 1-phenyl-3-pyrazolidone, l-ptolyl-3-pyrazolidone, 5-phenyl-3pyrazolidone, l-pchlorophenyl-3-pyrazolidone, 1-m-tolyl-3-pyrazolidone, lphenyl-5-methyl-3-pyrazolidone, l-p-tolyl-S -phenyl-3- pyrazolidone, 1-p-methoxyphenyl-3-pyrazolidone, lacetaminophenyl-3-pyrazolidone, l-m-aminophenyl-4- methyl-4-propyl-3-pyrazolidone, l-3-acetaminophenyl-4,4- diethyl- 3-pyrazolidone, l-p-tolyl-4,4-diemthyl-3- pyrazolidone, etc. Other developing agents include catechol; pyrogallol; paraminophenol; diaminophenol; paraphenylenediamine; monomethyl paraminophenol; halogenated acyl derivatives of a 1,4-dihydroxy benzene as disclosed in U.S. Pat. No. 3,246,988; N-acyl derivatives of an aminophenol as disclosed in U.S. Pat. No. 3,291,609; etc.

The developing agents noted above, in combination with silver halide emulsion are coated onto a supporting material' using known prior art coating procedures. Suitable supports include rag content paper, pulp paper, plastics such as, for example, polyethylene terephthalate (Mylar), cellulose acetate, metallic foil and glass. The support may be in any form such as, for example, sheets and rolls.

The photographic elements comprising the silver halide emulsion in combination with a developing agent are exposed to a suitable original or record and developed by merely treating the exposed emulsion layer with the alkaline activator solutions of this invention. A typical activator bath comprises, for example an aqueous solution of an alkaline material such as sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, and mixtures with sodium sulfite and from 2 to 20 grams/liter of a thiosulfate, preferably a thiosulfate selected from the group of alkali and alkaline earth metal thiosulfates and ammonium thiosulfate. Sodium thiosulfate and ammonium thiosulfate are especially preferred because of their increased solubility in an aqueous solution. The activator solution should be adjusted by the addition of alkaline material to a pH of at least 9.0 and preferably of at least about 10.5.

The activator solutions of the present invention can be applied to an exposed photographic element in any number of ways, such as by dipping, spraying, or other suitable surface applications. If desired, a thickener can be added to the activator solution to increase the viscosity of the composition and make it more adaptable for continuous processing. Viscous compositions can then be removed by squeegeein g or water spraying. The photographic element can then be stabilized by conventional fixation or stabilization, such as by contact with sodium thiosulfate, ammonium thiocyanate, etc.

Though not wishing to be bound by theory, it is believed that the thiosulfate in the activator increases image density by causing unexposed silver halide to dissolve and plate on the image area simultaneously with chemical development, thereby creating a blue-black image tone of increased maximum density and sharpness.

The invention, above described, is exemplified as follows:

EXAMPLE 1 A photographic element comprising a positive, high speed silver bromide emulsion containing a hydroquinone developing agent coated onto a document weight paper support was exposed to an image pattern from a tungsten light source for about zfi-second duration, thereby giving an exposure of about 400 meter candle seconds.

An activator solution was applied to the thus exposed photographic element by passing the element between coated applicator rolls. The activator solution was of the following composition:

Sodium Hydroxide 40 grams NaOH) Sodium Sulfite 20 grams Sodium Thiosulfate grams r i a' g Water to make 1 liter of solution.

A sharp visible image was produced in about 3 seconds. The photographic element with the coating of activator solution was then immediately immersed in a stabilizer solution comprising 150 grams per liter of ammonium thiocyanate for about one second, squeegeed and allowed to air dry. The developed print was sharp and possessed a blue-black image tone. it was then tested on a Macbeth densitometer and found to have a densitometer reading of 1.42.

EXAMPLE 2 The procedures of example 1 was repeated with the substitution of an activator solution free of a thiosulfate having the following composition:

Sodium Hydroxide 40 grams (NaOH) Sodium Sulfite grams Water to I liter.

EXAMPLE 3 The photographic element of example 1 was exposed to an image pattern from a tungsten light source for about -second duration to provide an exposure of about 400 meter candle seconds.

An activator solution was applied to the exposed photographic element by passing the element between coated applicator rolls. The activator was of the following composition:

Sodium Hydroxide 40 grams (NaOH) Sodium Sulfite 20 grams (Na,SO,)

Ammonium Thiosullule 2 grams 4 lx r sl Water to 1 liter.

A sharp visible image was produced in about 3 seconds. The photographic element was immediately immersed in a stabilizer bath comprising grams per liter of ammonium thiocyanate for about 1 second, squeegeed and allowed to air dry. The print obtained by this process had a sharp, blue-black image with a maximum density of 1.40 as tested on a Macbeth densitometer.

I claim:

1. In a process for developing a photographic image in an exposed light-sensitive silver halide emulsion, said emulsion having a silver halide developing agent therein or in an adjacent layer in intimate contact with said emulsion, wherein said process comprises applying to said exposed silver halide emulsion an alkaline activator solution having a pH of at least about 9 (and containing a thiosulfate in an amount from):

the improvement comprising incorporating into said activator solution about 2 to about 10 grams per liter of a thiosulfate to increase image density in the light-exposed areas.

2. An improvement of claim 1 wherein said alkaline solution has a pH of at least about 10.5.

3. An improvement of claim 2 wherein said thiosulfate is selected from the group consisting of alkali metal thiosulfates, alkaline earth metal thiosulfates, and ammonium thiosulfate.

4. An improvement of claim 3 wherein said thiosulfate comprises sodium thiosulfate.

5. An improvement of claim 4 wherein said alkaline solution comprises an aqueous solution of said sodium thiosulfate and a alkaline material selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and mixtures thereof with sodium sulfite.

6. An improvement of claim 5 wherein the developing agent is a member selected from the group consisting of hydroquinone and substituted hydroquinones.

7. An improvement of claim 1 wherein said alkaline solution comprises an aqueous solution of sodium hydroxide and a thiosulfate.

8. An improvement of claim 1 wherein said alkaline solution comprises an aqueous solution of sodium hydroxide sodium sulfite and sodium thiosulfate.

9. In a process for photographic reproduction comprising:

a. exposing a photographic element comprising a light-sensitive silver halide emulsion having a silver halide developing agent therein or in an adjacent layer in intimate contact with said silver halide emulsion;

. subsequently applying an alkaline activator solution having a pH of at least about 9 to said photographic element to develop a photographic image therein; and

c. subsequently contacting said photographic element with a fixing solution, the improvement comprising incorporating into the activator solution about 2 to about 10 grams per liter of a thiosulfate to increase image density in light-exposed areas.

10. A process of claim 9 wherein said alkaline solution has a pH of at least about 10.5.

11. A process of claim 10 wherein said thiosulfate is selected from the group consisting of alkaline metal thiosulfates, alkaline earth metal thiosulfates and ammonium thiosulfate.

12. A process of claim 11 wherein said thiosulfate comprises sodium thiosulfate.

13. A process of claim 12 wherein said solution comprises an aqueous solution of sodium thiosulfate and an alkaline material selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate and mixtures thereof with sodium sulfite.

14. A process of claim 13 wherein said alkaline material comprises sodium hydroxide.

15. A process of claim 13 wherein said alkaline material comprises a mixture of sodium hydroxide and sodium sulfite.

16. A process of claim 11 wherein said thiosulfate comprises ammonium thiosulfate.

Disclaimer 3,622,332.Jo7m R. Kane, Pifi'ard, N.Y. PHOTOGRAPHIC PROCESS WITH IMPROVED ACTIVATOR COMPOSITION. Patent dated Nov. 23, 1971. Disclaimer filed May 30, 1972, by the assignee, Itek Corporation. Hereby enters this disclaimer to all claims of said patent.

[Ofiicz'al Gazette August 15,1972] 

2. An improvement of claim 1 wherein said alkaline solution has a pH of at least about 10.5.
 3. An improvement of claim 2 wherein said thiosulfate is selected from the group consisting of alkali metal thiosulfates, alkaline earth metal thiosulfates, and ammonium thiosulfate.
 4. An improvement of claim 3 wherein said thiosulfate comprises sodium thiosulfate.
 5. An improvement of claim 4 wherein said alkaline solution comprises an aqueous solution of said sodium thiosulfate and a alkaline material selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and mixtures thereof with sodium sulfite.
 6. An improvement of claim 5 wherein the developing agent is a member selected from the group consisting of hydroquinone and substituted hydroquinones.
 7. An improvement of claim 1 wherein said alkaline solution comprises an aqueous solution of sodium hydroxide and a thiosulfate.
 8. An improvement of claim 1 wherein said alkaline solution comprises an aqueous solution of sodium hydroxide sodium sulfite and sodium thiosulfate.
 9. In a process for photographic reproduction comprising: a. exposing a photographic element comprising a light-sensitive silver halide emulsion having a silver halide developing agent therein or in an adjacent layer in intimate contact with said silver halide emulsion; b. subsequently applying an alkaline activator solution having a pH of at least about 9 to said photographic element to develop a photographic image therein; and c. subsequently contacting said photographic element with a fixing solution, the improvement comprising incorporating into the activator solution about 2 to about 10 grams per liter of a thiosulfate to increase image density in light-exposed areas.
 10. A process of claim 9 wherein said alkaline Solution has a pH of at least about 10.5.
 11. A process of claim 10 wherein said thiosulfate is selected from the group consisting of alkaline metal thiosulfates, alkaline earth metal thiosulfates and ammonium thiosulfate.
 12. A process of claim 11 wherein said thiosulfate comprises sodium thiosulfate.
 13. A process of claim 12 wherein said solution comprises an aqueous solution of sodium thiosulfate and an alkaline material selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate and mixtures thereof with sodium sulfite.
 14. A process of claim 13 wherein said alkaline material comprises sodium hydroxide.
 15. A process of claim 13 wherein said alkaline material comprises a mixture of sodium hydroxide and sodium sulfite.
 16. A process of claim 11 wherein said thiosulfate comprises ammonium thiosulfate. 